1. Field of the Invention
This invention relates to an antenna for wireless communications, and more particularly to a PCMCIA antenna for wireless communications. In particular, the antenna of this invention is designed to provide a compact, portable, full-performance antenna on a small platform of a PCMCIA card which has the same performance as a 6.5 inch long 1/2 wave antenna, thereby providing greater flexibility, portability and product marketing ability.
2. Description of the Related Art
This invention relates to antennas for use with wireless data communications, and portable communications in general, that typically use the PCMCIA (Personal Computer Memory Card Interface Association) Standards. These devices are commonly used with portable computing devices including, but not limited to, palm-top computers, lap-top computers, PDA (personal digital assistants) and/or other devices developed to enhance productivity. The limitation of these devices is current interface with an existing host computer system to exchange data requiring a hard-wire telephone line. This, however, does not work well with an individual who is, for example, travelling, typical of a salesperson. This invention is used with wireless communication modules that can be interfaced with the PCMCIA socket on one of the aforementioned devices. These wireless modules will transmit and/or receive data from selected sites to provide updates for information and real-time access to data. Because of this communication technology, the antenna is required to accomplish this feat.
The most popular frequencies for these types of applications are currently between 806 MHz and 941 MHz, although this concept may be used on a wide variety of frequencies. The PCMCIA card, with its physical size expressed as a function of wave length, requires an antenna significantly larger than the PCMCIA form factor will allow. Therefore, it is necessary to have an antenna which can be extended to maintain maximum performance and minimize the ground plane and shielding effects of the host device as additional frequencies become available for wireless LAN, WAN or for other applications, up to and including 5.8 GHz.
The only products that are currently being offered for this particular application of which applicants are aware, are helically loaded monopoles. Radiation patterns the helically loaded monopoles are influenced by the ground plane offered by the host device. They also induce RF currents on the chassis which can create problems, interference, etc., with RF currents, desensitization and RF currents flowing on the case that affect both the RF circuit and the digital logic circuit inside of the host device and the PCMCIA platform.